A keyboard is a widely-used input device of a computer. Generally, a keyboard has a plurality of key structures. FIG. 1 is a schematic perspective view illustrating a key structure of a keyboard according to the prior art. When the key structure 1 is depressed, a corresponding switch is triggered to generate an electronic signal to the computer.
FIG. 2 is a schematic exploded view illustrating a key structure according to the prior art. As shown in FIG. 2, the key structure 1 comprises a keycap 11, a scissors-type support member, an elastic element 14, a membrane switch 15 and a base plate 16. The scissors-type support member comprises an inner frame 12 and an outer frame 13. The inner frame 12 and the outer frame 13 cooperate with each other to fix the keycap 11 on the base plate 16. The membrane switch 15 is disposed on the base plate 16. The elastic element 14 is arranged between the keycap 11 and the membrane switch 15. When the keycap 11 is depressed, the elastic element 14 is deformed downwardly to trigger the membrane switch 15 such that the membrane switch 15 generates an electronic signal. In designing the scissors-type support member, the keycap 11 should be returned to its original position after the depressing force exerted on the keycap 11 is eliminated. Generally, the elastic element 14 provides the restoring force to push the keycap 11 back to its original position. Moreover, the inner frame 12 and the outer frame 13 should cooperate with each other in order to precisely control the upward moving action of the keycap 11. In other words, the configurations of the inner frame 12 and the outer frame 13 are very important factors that influence the quality and the use life of the key structure 1.
Please refer to FIG. 2 again. Two pivot rods 121 are formed on the arm part of the inner frame 12. Corresponding to the pivot rods 121, two pivot holes 131 are formed on an arm part of the outer frame 13. The pivot rods 121 are pivotally coupled with the pivot holes 131 such that the inner frame 12 is rotatable on the outer frame 13. For combining the inner frame 12 with the outer frame 13, the user needs to prop open the arm part of the outer frame 13 to widen the distance between these two pivot holes 131. As such, the pivot rods 121 could be successfully inserted into corresponding pivot holes 131 so as to combine the inner frame 12 and the outer frame 13 together. The process of propping open the outer frame 13 is time-consuming and thus detrimental to the throughput of the keyboard. On the other hand, if the external force used to prop open the outer frame 13 is improper, the outer frame 13 is readily damaged and the yield is reduced.
Please refer to FIG. 2 again. After the inner frame 12 and the outer frame 13 of the conventional key structure 1 are combined together, the pivot rods 121 are pivotally coupled with the pivot holes 131. For maintaining stability of the keycap 11 and preventing from the rocking condition of the keycap 11 during the keycap 11 is depressed or returned to its original position, the pivot rods 121 need to be tightly fitted into corresponding pivot holes 131. Since the pivot rods 121 are tightly fitted into corresponding pivot holes 131, a strong friction force is generated when the inner frame 12 is rotated with respect to the outer frame 13. Under this circumstance, the tactile feel upon depressing the keycap 11 is deteriorated. After the keycap 11 has been depressed for many times, the regions between the pivot rods 121 of the inner frame 12 and the pivot holes 131 of the outer frame 13 are readily abraded by the friction force. That is, the pivot rods 121 will no longer be tightly fitted into corresponding pivot holes 131. Finally, the keycap 11 is unstable and easily rocked.
Therefore, there is a need of providing a scissors-type support member capable of maintaining stable movement of the keycap and achieving a desired tactile feel when the keycap is depressed. Moreover, the inner frame and the outer frame of the scissors-type support member should be easily assembled without the need of propping open the outer frame.